In current radio communication environments, cellular networks are required to process more and more data as various devices, such as smartphones or tablet PCs, appear and spread, which require a high data transmission rate.
To meet such demand for high data rate, communication technologies are advancing toward carrier aggregation and cognitive radio technologies to effectively utilize more frequency bands and multi-antenna and multi-base station cooperation technologies to raise data capacity in a limited frequency range. Further, the communication environment evolves to have increasing density of nodes to which a user can gain access.
A system with such high density of nodes may exhibit higher system capacity thanks to inter-node cooperation. Such scheme shows much higher capacity than when each node operates as an independent base station (e.g., base station (BS), Advanced BS (ABS), Node-B (NB), eNode-B (eNB), or Access Point (AP)) without cooperation.